Recto: The cranium sectioned. Verso: The skull sectioned

A drawing of a skull viewed obliquely from above and the left, which shows the intracranial nerves and vessels. With notes below on the importance of the cranium as the seat of all nervous activities, in Leonardo’s characteristic ‘mirror-writing’, left-handed and moving from right to left. The drawing on the verso of this sheet shows the skull sawn first down the middle, then across the front of the right side. With the two halves juxtaposed, the viewer can locate the facial cavities in relation to the surface features – the frontal sinus within the brow, the orbit of the eye, the nasal cavity, the maxillary sinus in the cheek, and the mouth. Leonardo believed all except the frontal sinus to be a third of the depth of the skull, each terminating below the senso comune. In the left margin Leonardo drew, described and enumerated the different types of teeth, molar, premolar, canine and incisor. Leonardo’s most brilliant and sustained scientific pursuit was his study of human anatomy. He made hundreds of drawings from corpses that he had dissected in monastery hospitals, recording many anatomical structures for the first time in medical history. Text adapted from Leonardo da Vinci: A life in drawing, London, 2018